The British former boss of GlaxoSmithKline in China will be deported back to the UK after pleading guilty to bribery-related charges and being handed a three-year suspended prison sentence.

Mark Reilly had been barred from leaving China for the past year and accused of overseeing a "criminal godfather" scheme to bribe doctors with £300m worth of cash and sex to prescribe GSK drugs.

On Friday Reilly was given a three-year jail term suspended for four years, following a one-day trial behind closed doors in Changsha, in southern China's Hunan Province. But it is unclear whether Reilly, who remains a GSK employee, will have to serve out the four-year period in China before he is sent back to Britain.

GSK said it was urgently trying to clarify the sentence and ensure his immediate return to the UK. A Chinese government source was quoted as saying Reilly "will be deported so he won't be in detention in China".

Four other senior Chinese GSK executives were also handed suspended sentences of between two and four years.

The company was fined £300m after the court found that Britain's biggest drugs company had "offered money or property to non-government personnel in order to obtain improper commercial gains".

After the verdict GSK issued an "apology to the people of China" and said it had "reflected deeply and learned from its mistakes".

"GSK sincerely apologises to the Chinese patients, doctors and hospitals, and to the Chinese Government and the Chinese people. GSK deeply regrets the damage caused. GSK also apologises for the harm caused to individuals who were illegally investigated by GSK China Investment company," it said.

Andrew Witty, GSK's chief executive, said: "Reaching a conclusion in the investigation of our Chinese business is important, but this has been a deeply disappointing matter for GSK. We have and will continue to learn from this. GSK has been in China for close to a hundred years and we remain fully committed to the country and its people.

"We will continue to expand access to innovative medicines and vaccines to improve their health and well-being. We will also continue to invest directly in the country to support the government's health care reform agenda and long-term plans for economic growth."

Witty took a £245,000 cut to his bonus for last year specifically related to the corruption scandal, but that was in the context of a total pay and shares package of £6.5m, of which the bonus made up £1.9m.

GSK could face further fines from the UK's serious fraud office and US department of justice, which are both investigating bribery allegations that also stretch to Poland, Iraq, Jordan and Lebanon.

The company said it had fundamentally changed the incentive programme for its sales force, and increased the monitoring of invoicing and payments.

When the Chinese authorities began their investigation into the claims last year Gao Feng, the head of China's fraud unit, said: "We found that bribery is a core part of the activities of the company. To boost their share prices and sales, the company performed illegal actions."

GSK was alleged to have used a network of more than 700 middlemen and travel agencies to bribe doctors and lawyers with cash and even sexual favours. "There is always a big boss in criminal organisations, and in this case GSK is the big boss. In order to win the favour of GSK, some travel agencies don't just offer money to their executives but also sexual bribes," Gao said.

The scandal erupted into the public domain after a covertly filmed sex video of Reilly with his Chinese girlfriend was emailed to Witty and other GSK board members in an apparent blackmail attempt.

Accompanying the footage were detailed allegations of sales and marketing practices described as "pervasive corruption" by someone calling themselves "GSK whistleblower".

When the sex video surfaced, GSK hired a British corporate investigator, Peter Humphrey, to find out who broke into Reilly's apartment. In July last year Humphrey and his wife and business partner, American citizen Yu Yingzeng, were arrested by Chinese police over charges that they had illegally bought and sold personal data of Chinese citizens.